In Exchange, we rebooted our servers in the lab and once they started up, one of the Exchange 2019 Servers was showing a ServiceDown error when checking the DAG status in Powershell.
The error is easy to fix but you can view more information on it by typing the following command:
- Get-MailboxDatabaseCopyStatus | fl
As you can see above the replication service is not started. Head over to Services.msc and you can see of all the services that one failed to start:
Once you start it and then run the above command (without the fl) it should show the database as mounted:
Hope it helps.